Compositional dependence of the exciton reduced mass in GaAs_1-xBi_x (x=0-10%), G. Pettinari, A. Polimeni, J. H. Blokland, R. Trotta, P. C. M. Christianen, M. Capizzi, J. C. Maan, x. F. Lu, E. C. Young, T. Tiedje, Phys. Rev. B 81, 235211 (2010)

We report the compositional dependence of the exciton reduced mass, μexc, of GaAs_1-xBi_x in a very large Bi concentration range (x=0-10.6%). Photoluminescence under high magnetic fields (B up to 30 T) shows that μ _exc increases rapidly until x∼1.5% and then oscillates around ∼0.08 m₀, m₀ being the electron mass in vacuum, up to about x=6%. Surprisingly, for x>8% the exciton reduced mass decreases below the GaAs value, in agreement with the expectations of a k⋅p model. Such a behavior reveals the existence of different concentration intervals, where continuum states of the valence and conduction band hybridize with Bi-related levels at different extents, thus conferring to the band edges a localized or bandlike character for x<6% and x>8%, respectively.